Support arm for desk lamp



FIG. 1 is a perspective view thereof;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a right side view, the left side view being identical;

FIG. 4 is a top view thereof; and,

FIG. 5 is a bottom plan view thereof.

The broken lines shown in the drawing are environmental only and form no part of the claimed design. 

The ornamental design for a support arm for desk lamp, as shown and described. 